Age related macular degeneration (AMD) is a condition found in elderly adults in which the macula area of the retina suffers thinning, atrophy and bleeding. This results in the loss of vision in the central area of vision, particularly an inability to see fine details, to read or to recognise faces.
AMD is classified as either dry (non-neovascular) or wet (neovascular). Wet AMD involves the growth of new blood vessels in an area where they are not supposed to be. The dry form is more common than the wet, with about 85-90 percent of AMD patients diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss.
Dry AMD is an early stage of the disease, and may result from the aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes. Dry macular degeneration is diagnosed when yellowish spots known as drusen begin to accumulate from deposits or debris from deteriorating tissue primarily in the area of the macula. Gradual central vision loss may occur with dry macular degeneration.
Dry AMD can progress to wet AMD, in which new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells, which die off and create blind spots in central vision.
Treatments for AMD are at present limited, but some treatments may delay its progression or improve vision. Treatments for macular degeneration depend on whether the disease is in its early stage or dry form or more advanced, wet form that can lead to serious vision loss. One treatment method is the transplantation of cells from the healthy periphery of the eye in patients with wet AMD into the affected area. Whilst this is effective, there is a limit to the size of the affected area that can be treated and the operation is long and inappropriate for most elderly patients. It would be advantageous to provide improved treatments for both forms of AMD.
The inventors have investigated ways that replacement retinal epithelial cells may be obtained and transplanted, in particular using stem cells to produce the required cells. The inventors have developed a membrane on which such cells may be grown and which may be transplanted into the eye, along with the cells. The membrane is particularly useful for the growth of retinal pigmented epithelial (RPE) cells and derivatives thereof, but other cells types may also be grown.
Previously, cells have been grown on membranes. Williams et al., (Journal of Materials Science: Materials in Medicine 16 (2005) 1087-1092) have used polyurethane membranes to culture RPE cells, but have found that the surface of the membranes usually requires treatment to enable cell attachment. Other groups have used polyester membranes.